Revisit the default behaviour of job parameters conversion

[fmbenhassine]

The current behaviour of the DefaultJobParametersConverter has been confusing in many situations:

• The way to specify parameter types with the parameter(type)=value notation is not friendly to command line arguments and environment variables
• The way to specify identifying / non identifying job parameters with +/- prefixes is not friendly with Spring Boot

While it is possible to provide a custom JobParametersConverter and set it on the CommandLineJobRunner or JobOperator, I believe the default behaviour should be reviewed for a better getting started experience for batch users and a better integration with Spring Boot. Since this could be a breaking change, I see v5 as a good opportunity to revisit this part of the framework.

References:

• https://stackoverflow.com/questions/66302293/spring-batch-job-param-always-show-zsh-no-matches-found
• Task status is Unknown when using exec as entry point style spring-attic/spring-cloud-dataflow#4291
• Add a property to all for Batch JobParameters to enable configuration via environment variables spring-boot#23411

Related issues:

• New JobParameter Types Required [BATCH-1581] #1983
• Parameter types improvement #2122

[lcmarvin]

Any update on this, how to define the default parameter's format?

[lcmarvin]

@benas Is it possible to add a command line option like -parameterFile to specify the path of job parameters file? This file could be .json, .properties or .ymal. For example,

[
    {
        "job":"fooJob",
        "parameters":[
            {
                "parameterName":"k1",
                "parameterType":"String",
                "paramter":"v1"
            },
            {
                "parameterName":"k2",
                "parameterType":"Long",
                "paramter":123,
                "identifying":true
            }
        ]
    }
]

spring.batch.job.parameters.fooJob[0].parameterName=k1
spring.batch.job.parameters.fooJob[0].parameterType=String
spring.batch.job.parameters.fooJob[0].parameter=v1
spring.batch.job.parameters.fooJob[1].parameterName=k2
spring.batch.job.parameters.fooJob[1].parameterType=Long
spring.batch.job.parameters.fooJob[1].parameter=123
spring.batch.job.parameters.fooJob[1].identifying=true

spring:
  batch:
    job:
      parameters:
        fooJob:
          - parameterName: k1
            parameterType: String
            parameter: v1
          - parameterName: k2
            parameterType: Long
            parameter: 123
            identifying: true

I think this format may be more friendly for Spring Boot users, compared with parameter(type)=value and +/-.